I own a TA31, and a TAO1nsn. I do own a Dr Optics, but it is on top of my SPR, not my TAO1nsn. So while I havent used the TAO1nsn + Dr Optics combo, I have used all three sighting systems you are asking about.
I would give away all the others before I took the TA31 off my rifle. You're right, I did ay the TA31 is a compromise, but *everything* is a compromise. I have an Aimpoint as well, and for CQB I like nothing better. But it is a compromise as well. Its simplicity and idiot proof design are also inherant to its limitations.
Anyhow... phoria is the difference in POA/POI from the magnified and unmagnified view in ACOGs. I know that just how much difference it is can more or less extreme for different people. Like Duff, it is rather slight for me. For all the reasons Duff's already gone over, its never been enough to really make a difference one way or the next.
I will say that head position is more critical on a TA31 than with something like a unmagnified dot sight, but I think I read in wither this post or another where you implied that you have to be rock solid behind the optic to use it. This isnt true. You have some play in where your head can be, just not as much play. With a TA11, you have even more play. Neither as much as a unmagnified optic, but still some, and TA11 even more so than the TA31. Also, consider this. One thing thats suprised me with the Dr Optics set up is a lack of flexibility with head alignment. Becasue the window of the Dr Optics unit is so small, I find that if I move my head around too much, I wont be looking through the window. This may have something with how far out the Dr Optics is on my SPR, but it suprised me.
Having the Dr Optics zerod at close range will help with the height over bore problems ACOGs have. At close ranges you do have to aim high to put the hits where you want them. To me, this one advantage is not enough for me to even consider switching set ups.
Weird shooting positions has been an issue, but it is nothing you cant work with. I've used my TA31 in the last two or three classes I've taken and there were a couple instances where the instructors we having us shoot from odd positions that the Aimpoint would have been better... in these SPECIFIC instances. But it wasnt anything I couldnt overcome quickly with a slight shift in my shooting position.
Put it this way. I feel like the TA31and TA11 are probably the best overall optic you can look for. Even though I dont own a TA11 I have used them lots so I feel like I can include them in my opinion. They are not the easiest things to use and there is a few things you have to know about them and take into consideration during use. However, if you take the time to use it a lot and work it, the optic will work wonders for you. If all you have is a TAO1 series optic, the Dr Optics set up is a much better system than just the ACOG alone. But I dont think it beats the BAC.
I would take them over a TAO1 series + Dr Optic set up for the following reasons. Its a much simpler, more robust set up. I dont really like the fact that I'd have to switch from the Dr Optics to the ACOG for short and long targets after knowing how easy it is to do with a single optic. Id rather aim a little high at close ranges than constantly switching head positions. I realize you gave several specific instances to show how switching isnt a problem for you. For me, I'd rather keep a more flexible and fluid shooting style. The courses we fire at FDCC are always changing and demanding. Im constantly having to go from quick CQB shots to longer shots or shots that require more precision. The thought of having to keep bobbing my head up and down to do so just makes me cringe.